In recent years, a technology has been put to practical use that installs multiple cameras in a moving object such as a vehicle to provide captured images surrounding the vehicle for a driver or the like. For example, technologies such as a wrap-around view monitor are available. In an on-board multi-camera system, images surrounding a vehicle are provided by synthesizing images with multiple cameras. Also, in such an on-board multi-camera system, calibration of the installed cameras is executed to obtain high-quality synthesized images.
Here, calibration means to estimate the installed position of a camera relative to the vehicle (three degrees of freedom, for example, X, Y, and Z) and its orientation (three degrees of freedom, for example, tilt angle, roll angle, and pan angle).
As a calibration method, for example, a marker is installed at a known position surrounding a vehicle to estimate the position and orientation of a camera using a relationship between the physical position of the marker and a position of the marker in a camera image. This method requires, however, a special-purpose environment (for example, a vehicle factory) to install a marker at a known position surrounding a vehicle. Therefore, it is difficult for a user to easily execute calibration of a camera within a short time.
Thereupon, a technology has been devised that makes it possible to execute calibration easily within a short time without requiring a strict installation of a marker. For example, with such a technology, calibration is executed with images that capture jigs placed at predetermined positions surrounding a vehicle so that image capturing ranges of multiple cameras are overlapping at the positions of the jigs. Each of the jigs has a marker which is applied with a known process with other markers (see, for example, Patent Document 1).